This research will investigate an insect neurohormone that affects the levels of cytochromes aa3 and/or b in fat body mitochondria of adult Blaberus discoidalis cockroaches. Through its effects on cytochrome levels, the neurohormone may regulate the energy level and metabolic capacity of the insect fat body. The fat body is the principal biosynthetic tissue of the insect so that regulations of its metabolic capacity influence other physiological processes such as reproduction that depend on the fat body for biosynthetic products. These studies will undertake the isolation and chemical characterization of the neurohormone. The cellular action of the neurohormone will be investigated by identifying the affected cytochromes and determining whether the hormone regulates heme or apoprotein synthesis. Finally, the physiological significance of the neurohormone will be studied by determining its regulatory effects on the synthesis and degradation of the fat body mitochondrial cytochromes and its possible influence on reproductive metabolism in adult insects.